For optical apparatuses such as a digital camera and a digital video, solid-state image sensing device such as a Charge Coupled Device (CCD) image sensor and a Complementary Metal Oxide Semiconductor (CMOS) image sensor are used. However, spectral characteristics of the solid-state image sensing devices have high sensitivities with respect to infrared light as compared to human visibility characteristics. Hence, spectral correction by a near-infrared cut filter is performed in the optical apparatus having the solid-state image sensing device.
As the near-infrared cut filter, for example, a near-infrared absorption type color glass filter such as fluorophosphate-based glass containing Cu2+ ions as a coloring component, a multilayer film filter in which an optical multilayer film for blocking near-infrared light and ultraviolet light is provided on a transparent base material, and further a filter combined with them have been used.
The optical multilayer film is required to cause no phenomenon of decreasing in transmittance (ripple) in a transmission band at 400 nm to 700 nm that the solid-state image sensing device requires. Conventionally, there has been known a technique of suppressing occurrence of a ripple in the optical multilayer film (see, for example, Patent References 1 (JP-B 4672101) and 2 (JP-A 2008-139693)).